The corticotropin-releasing hormone (CRH) system, consisting of CRH, urocortins (Ucns), their receptors CRH(1) and CRH(2), and CRH-binding protein, holds the principal role in mediating the response to stress stimuli. Besides their expression in the brain, CRH neuropeptides and receptors have been found in multiple peripheral sites. We investigated the expression of the CRH system in the human liver, using RT-PCR and immunohistochemistry. Ucn 1 gene transcripts were amplified in all the human liver biopsies examined. Ucn 1 immunoreactivity was localized in hepatocytes. CRH(1) and CRH(2(alpha)) receptor gene expression was also found, and receptor protein had a similar distribution to Ucn 1. Finally, Ucn 1 and CRH receptor expression was demonstrated in hepatic biopsies from a variety of liver pathologies, including primary or metastatic liver carcinoma and cirrhosis. We conclude that the CRH system is expressed by human liver under normal and pathological conditions, Ucn 1 being the major ligand. Further study is required to unfold the biological role of these effectors in liver physiology and pathogenesis, as they may act in an autocrine manner through activation of the CRH receptors expressed locally.